In wire-in-channel superconductive conductors, a superconducting wire is soldered into a normally-conductive channel of a corresponding dimension. FIG. 1 is an illustration of a conventional wire-in-channel superconductor 10. Superconducting wire 12 typically consists of a number of filaments 14 of a superconducting material, such as NbTi, in a normally-conductive matrix material 16, such as copper. Such a superconductive wire 12 is soldered 18 into a corresponding groove in conductive channel 20. The channel 20 is typically of copper, and typically has an approximately rectangular cross-section. The external surface of the channel 20 may be tinned, for example with a suitable solder.
Such wire-in-channel superconductive conductors have been found effective in achieving long continuous lengths, and in providing a superconductive conductor which is suitable for persistent magnets. Wire-in-channel superconductive conductors of this type are typically insulated by a polyester braid 24.
The known copper channel wire-in-channel type superconductive conductor 10 is designed to provide a high copper-to-superconductor ratio, for stability, without the necessity of processing all of the copper with the superconductor. As a result, the cost of production is significantly reduced as compared to methods of production which require processing all of the copper with the superconductor.
Because of the large quantity of material used in the conductive channel in many applications, it is desirable to reduce the weight of the channel 20 and also to make it more pliable for ease in magnet fabrication. Aluminum is an excellent substitute material for the usual copper, being less costly, more pliable and lighter in weight; however, the use of aluminum as a direct substitute for copper presents several manufacturing difficulties such as quality of solder bond, soldering temperature and compatibility of fluxes as well as the flexibility of the completed wire-in-channel conductor. Accordingly, aluminum has not been used as a direct substitute for the copper material normally used for the channel 20 shown in FIG. 1.
Japanese patent application JP04071112A describes an arrangement in which an aluminum channel 20 is formed, and at least the interior of the groove 22 is coated in copper by a process such as electroplating, dipping or vapour deposition. The superconducting wire is then soldered 18 onto the copper coating within the groove 22, the resulting composite material then being subjected to a drawing process.